1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a thin film patterning apparatus and method of fabricating color filter array substrate using the same. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for a thin film patterning apparatus that can perform a patterning process without using a photolithography process.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) controls the light transmissivity of liquid crystal by use of an electric field, thereby displaying a picture. The liquid crystal display device includes a liquid crystal display panel in which liquid crystal cells are arranged in a matrix form, and a driving circuit for driving the liquid crystal display panel. In the liquid crystal display panel, a reference electrode, such as a common electrode, and pixel electrodes are provided for applying the electric field to each of the liquid crystal cells. Generally, the pixel electrodes are formed on a lower substrate in individual liquid crystal cells, and the common electrode is integral and formed over the entire surface of the upper substrate. The pixel electrodes are connected to thin film transistors TFT, which are used as switching devices. The pixel electrodes along with the common electrode drives the liquid crystal in accordance with a data signal supplied through the TFT.
FIG. 1 is an expanded perspective view of a related art liquid crystal display panel. Referring to FIG. 1, the related art liquid crystal display panel includes a color filter array substrate 10 and a thin film transistor array substrate 20, which are bonded together. Liquid crystal molecules 8 are between the color filter array substrate 10 and the thin film transistor array substrate 20. The liquid crystal molecules 8 rotate in response to the data signal applied to it, thereby controlling the amount of light transmitted through the thin film transistor array substrate 20.
The color filter array substrate 10 includes a color filter 4, a black matrix 2 and a common electrode 6, which are formed on the rear surface of the upper substrate 1. The color filter 4 includes red (R), green (G) and blue (B) color filters to enable a full color display. The black matrix 2 is formed between the adjacent color filters 4 to absorb the light from the adjacent cells, thereby preventing deterioration in the contrast.
The thin film transistor array substrate 20 has a data line 18 and a gate line 12, which are formed to cross each other. A gate insulating film (not shown) is formed over the gate line 12 and over the entire surface of a lower substrate 21. A TFT 16 is formed adjacent to where the data line 18 and the gate line 12 cross. The TFT 16 includes a gate electrode connected to the gate line 12, a source electrode connected to the data line 18, a drain electrode connected to the pixel electrode 14 and an active layer with a channel part. The active layer contacts the source and drain electrodes with ohmic contact layers. The TFT 16 selectively supplies a data signal from the data line 18 to the pixel electrode 14 in response to a gate signal from the gate line 12.
The pixel electrode 14 is located in a cell area that is defined by the data line 18 and the gate line 12, and is formed of a transparent conductive material with high light transmissivity. A potential difference is generated between the pixel electrode 14 and the common electrode 6 by a data signal supplied through the drain electrode. The potential difference causes liquid crystal molecules 8, which are located between the lower substrate 21 and the upper substrate 1, to rotate by dielectric anisotropy. Accordingly, the light supplied to the pixel electrode 14 from a light source is transmitted through the liquid crystal molecule 8 to the upper substrate 1.
Each pixel of the liquid crystal display panel shown in FIG. 1 includes a sub-pixel for realizing red (R), a sub-pixel for realizing green (G) and a sub-pixel for realizing blue (B). In the case of a pixel composed of R, G, B sub-pixels, only about 27%˜33% of the light emitted from a backlight is transmitted through the color filter 4. In order to solve such a problem, a color filter array substrate of the liquid crystal display panel having a different sub-pixel arrangement has been proposed.
FIG. 2 is a cross-sectional diagram of the related art color filter array substrate having a white color filter. The color filter array substrate of the liquid crystal display panel shown in FIG. 2 has red (R), green (G), blue (B) and white (W) sub-pixels 4R, 4G, 4W and 4B. In a liquid crystal display panel having the W sub-pixel, the amount of light emitted through the color filter 4 is greater than 85% of the light emitted from a backlight. Accordingly, the mean value of the light emitted from each pixel composed of the R, G, B, W sub-pixels is relatively high, thereby improving brightness.
FIGS. 3A to 3L are cross-sectional views representing a fabricating method of the related art color filter array substrate of the liquid crystal display panel shown in FIG. 2. First, an opaque layer 54, as shown in FIG. 3A, is formed on the upper substrate 1 by one of sputtering, spin coating and spinless coating. The opaque layer 54 is an opaque resin or an opaque metal, such as chrome (Cr) Subsequently, a photo resist pattern 52 is formed on the opaque layer 54 by a photolithography process using a first mask 50 that defines an exposure area S1 and a shielding area S2. The opaque layer 54 is patterned by an etching process using the photo resist pattern 52, thereby forming a black matrix 2 on the upper substrate 1, as shown in FIG. 3B.
A red resin 58, as shown in FIG. 3C, is spread over the whole surface of the upper substrate 1 on which the black matrix 2 is formed. Subsequently, the red resin 58 is patterned by a photolithography process using a second mask 56 that defines the exposure area S1 and the shielding area S2, thereby forming a red color filter 4R, as shown in FIG. 3D.
A green resin 60, as shown in FIG. 3E, is spread over the entire surface of the upper substrate 1 on which the red color filter 4R is formed. Subsequently, the green resin 60 is patterned by a photolithography process using a third mask 62 that defines the exposure area S1 and the shielding area S2, thereby forming a green color filter 4G, as shown in FIG. 3F.
A green resin 60, as shown in FIG. 3E, is spread over the entire surface of the upper substrate 1 on which the red color filter 4R is formed. Subsequently, the green resin 60 is patterned by a photolithography process using a third mask 62 that defines the exposure area S1 and the shielding area S2, thereby forming a green color filter 4G, as shown in FIG. 3F.
A blue resin 64, as shown in FIG. 3G, is spread on the entire surface of the upper substrate 1 on which the green color filter 4G is formed. Subsequently, the blue resin 64 is patterned by a photolithography process using a fourth mask 66 that defines the exposure area S1 and the shielding area S2, thereby forming a blue color filter 4B, as shown in FIG. 3H.
A white resin 68, as shown in FIG. 3I, is spread over the entire surface of the upper substrate 1 on which the blue color filter 4B is formed. The white resin 68 is an organic insulating material including an acrylic resin. Subsequently, the white resin 68 is patterned by a photolithography process using a fifth mask 70 that defines the exposure area S1 and the shielding area S2, thereby forming a white color filter 4W, as shown in FIG. 3J.
An organic insulating material is spread over the upper substrate 1 on which the white color filter 4W is formed, thereby forming an overcoat layer 22, as shown in FIG. 3K. Then, an organic material 76 is spread over the entire surface of the overcoat layer 22 on the upper substrate 1. Subsequently, the photo resist pattern 74 is formed by a photolithography using a sixth mask 72 that defines the exposure area S1 and the shielding area S2. The organic material 76 is patterned by the photo resist pattern 74, thereby forming a spacer 24, as shown in FIG. 3L.
A six mask process is required for forming the color filter array substrate shown in FIG. 2. In this case, costs are high because the fabrication process is complicated. Thus, there is a need for reducing manufacturing costs by simplifying the fabricating process.
FIG. 4 is an expanded perspective view representing a related art vertical alignment type liquid crystal display panel. The liquid crystal display device shown in FIG. 4 can realize a multi-domain by making the liquid crystal have several arrangement directions by using a rib 34. That is, in the vertical alignment type liquid crystal display panel shown in FIG. 4, the electric field applied to the liquid crystal is distorted by the rib 34, so that the liquid crystal is arranged in symmetric directions centered on the rib 34, thus the viewing angle is broadened.
FIGS. 5A to 5E are cross-sectional views for a fabricating method of the color filter array substrate shown in FIG. 4. Referring to FIG. 5A, the black matrix 2 is formed on the upper substrate 1. After the opaque resin or the opaque metal is spread over the upper substrate 1, the black matrix 2 is formed by patterning the opaque resin or the opaque metal by a photolithography process using a mask and etching process. The opaque resin can be, for example, carbon black, and the opaque metal can be, for example, chrome (Cr) or chrome oxide (CrOx/Cr/CrOx, CrOx/Cr/CrSix).
Referring to FIG. 5B, the color filter 4 is formed on the upper substrate 1 on which the black matrix 2 is formed. After each of red, greed and blue color resins is spread on the entire surface of the upper substrate 1 on which the black matrix 2 is formed, the color filter is formed by having each of the red, greed and blue color resins patterned by a photolithography process using a mask.
Referring to FIG. 5C, an overcoat layer 22 is formed over the upper substrate 1 on which the color filter 4 is formed. The overcoat layer 22 is formed by having a transparent insulating layer, such as acrylic resin or epoxy resin, spread over the entire surface of the upper substrate 1 on which the color filter 4 is formed.
Referring to FIG. 5D, a common electrode 6 is formed over the upper substrate 1 on which the overcoat layer 22 is formed. The common electrode 6 is formed by depositing a transparent conductive film, such as ITO or IZO, over the entire surface of the upper substrate 1 on which the overcoat layer is formed.
Referring to FIG. 5E, a rib 34 is formed over the upper substrate 1 on which the common electrode 6 is formed. After a polymer resin, such as acrylic resin or epoxy resin, is spread on the entire surface of the upper substrate 1 on which the common electrode 1 is formed, the rib 34 of polymer resin is formed by patterning through a photolithography process.
In the fabricating method of the related art vertical alignment type liquid crystal display panel, a plurality of patterns are formed by photolithography processes. The photolithography process is a series of photo processes including the steps of spreading photo resist, aligning masks, exposing and developing. The photolithography process has problems in that it requires a long time, a developing solution for developing the photo resist and too much photo resist pattern is wasted, and expensive exposure equipment is required. Further, the process of forming the rib 34 and the process of forming the overcoat layer 22 are separately performed, thus there is a problem in that the fabricating process time and the cost increases.